In the field of model aircraft exhaust mufflers, noise reduction is of particular importance to the model aircraft pilot in order to avoid creating excessive noise which may disturb residents in an area where the pilot enjoys flying his or her aircraft. It is important that such noise reduction is not provided at the cost of engine performance or the light weight of the aircraft. Model aircraft mufflers known in the art have typically been rudimentary, targeting only the basic requirement of lowering engine noise below 90 dB at 9 feet from the engine. Such an exhaust muffler kit is disclosed in U.S. Pat. No. 4,858,722 to Abbe et al.
In the area of small engine mufflers for such applications as motorcycles, snowmobiles and model vehicles, special designs have been provided to increase performance of the engine and ultimately reduce noise. Such exhaust systems are not particularly suitable for use with model aircraft due to complexity, size or configuration. For example, U.S. Pat. No. 4,531,364 to Equi discloses a compact expansion chamber for small engines of the type used on a model boat. In U.S. Pat. No. 4,046,219 to Shaikh, an exhaust muffler for a snowmobile is disclosed in which a conical expansion chamber terminates in a small end tube to which an absorptive spiral muffler unit is secured for attenuating high frequency exhaust noise. U.S. Pat. No. 3,703,937 to Tenney describes a multiple rpm range tuned exhaust pipe for two-cycle engines in which flow control is provided to vary the amount of back pressure in a manner conducive for proper engine performance in a motorcycle.